Chapter

1919Oceanography

The Blue Planet

19.1 The Seafloor

Nearly 71 percent of Earth’s surface is covered by the global ocean.

Oceanography is a science that draws on the methods and knowledge of geology, chemistry, physics, and biology to study all aspects of the world ocean.

Mapping the Ocean Floor

19.1 The Seafloor

The topography of the ocean floor is as diverse as that of the continents.

Bathymetry is the measurement of ocean depths and the charting of the shape or topography of the ocean floor.

Today’s technology—particularly sonar, satellites, and submersibles—allows scientists to study the ocean floor in a more efficient and precise manner than ever before.

The Topography of the Ocean

Continental Margins

19.1 Ocean Floor Features

In the Atlantic Ocean, thick layers of undisturbed sediment cover the continental margin. This region has very little volcanic or earthquake activity.

In the Pacific Ocean, oceanic crust plunges beneath continental crust. This force results in a narrow continental margin that experiences both volcanic activity and earthquakes

A continental margin is the zone of transition between a continent and the adjacent ocean basin floor.

Continental Margins

19.1 Ocean Floor Features

Continental Shelf• A continental shelf is the gently sloping

submerged surface extending from the shoreline.• Continental shelves contain important mineral

deposits, large reservoirs of oil and natural gas, and huge sand and gravel deposits.

Continental Margins

19.1 Ocean Floor Features

Continental Slope• A continental slope is the steep gradient that

leads to the deep-ocean floor and marks the seaward edge of the continental shelf.

Ocean Basin Floor

19.1 Ocean Floor Features

The ocean basin floor is the area of the deep-ocean floor between the continental margin and the oceanic ridge.

Ocean Basin Floor

19.1 Ocean Floor Features

Abyssal Plains• An abyssal plain is a very level area of the

deep-ocean floor, usually lying at the foot of the continental rise.

• The sediments that make up abyssal plains are carried there by turbidity currents or are deposited as suspended sediment settles out.

Seamounts and Guyots• A seamount is an isolated volcanic peak that

rises at least 1000 meters above the deep-ocean floor

• A guyot is an eroded, submerged seamount.

Abyssal Plain Cross Section

Mid-Ocean Ridges

19.1 Ocean Floor Features

A mid-ocean ridge is found near the center of most ocean basins. It is an interconnected system of underwater mountains that have developed on newly formed ocean crust.

Seafloor Spreading• New ocean floor is formed at mid-ocean ridges

as magma rises between the diverging plates and cools.

Subduction Zones

19.1 Ocean Floor Features

A subduction zone is a location where the ocean crust is pushed down into the mantle• Trenches form deep depressions

Web Site

19.1 Ocean Floor Features

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Energy Resources

19.1 Resources from the Seafloor

Oil and natural gas are the main energy products currently being obtained from the ocean floor.

• Metal deposits concentrated in areas of volcanic vents

Mineral deposits

• Some minerals precipitate out of seawater as conditions change

Manganese Nodules